Removing degeneracy and multimodality in gravitational wave source parameters

Quasicircular binary black hole mergers are described by 15 parameters, of which gravitational wave observations can typically constrain only $\ensuremath{\sim}10$ independent combinations to varying degree. In this work, we devise coordinates that remove correlations, and disentangle well- poorly-measured quantities. Additionally, identify approximate discrete symmetries in the posterior as primary cause multimodality, design a method tackle type multimodality. The resulting posteriors have little structure be sampled efficiently robustly. We provide python package for parameter estimation, cogwheel, implements these methods together with other algorithms accelerating inference process. One introduce is spin azimuth measured remarkably well several events. suggest might sensitive indicator orbital precession, anticipate it will shed light on occurrence spin-orbit misalignment nature.